Sculpting - Unwanted lines on brush strokes
As you said, it may be because of the low resolution.  Usually with Sculpting Mode, you'll want to use the Multiresolution modifier so that in sculpting mode you can have a high resolution while in object mode the resolution won't slow you down too much.  You can also check you brush settings, particularly Texture and Symmetry/Lock.  In Stroke settings, you can make sure that the spacing is set to 1% and the jitter to 0.